Ryan Mathews practiced Friday for the first time since a Raiders defender concussed him last Sunday. Mathews said it was his second concussion, but wasn't specific on when the previous one occurred or its severity. He said this one wasn't worse than the other one.

It appeared that Raiders linebacker Nick Roach kneed Mathews in the helmet, forcing him from the game in the second quarter. He had three carries for eight yards.

"Its just frustrating," Mathews said. "No one ever wants to get hurt. You don't want your brain to get messed with, either. It's frustrating that I didn't get a chance to be out there with my teammates and try to help them win, but it's part of the game."

The Chargers will practice again Saturday. Offensive coordinator Ken Whisenhunt wasn't definitive Friday when commenting on Mathews' availability for Monday night's game against the Colts.

"He's a powerful runner," Whisenhunt said. "To have Ryan back definitely would be a bonus."

Fluker practices

One day after not practicing, D.J. Fluker (calf) was a limited participant. King Dunlap practiced Thursday and Friday and seems on track to start Monday. Tackles Dunlap and Fluker last started together in Week Two, the 33-30 victory at Philadephia.

Butler didn't practice

Donald Butler (groin) didn't practice, and Mike McCoy said that owed to both maintenance and because of a flare-up in Thursday's practice. "I'm good. I just needed a day to rest. I'm getting my mental reps -- going through the calls, the same thing that you do on gameday," Butler said.